The Institute of Medicine (1998) noted that:1. Only a small proportion of substance abusers receive treatment.2. Of those who do receive treatment, the quality of care is highly variable and clients are not likely to receive an evidence-based treatment.3. Approximately 50% of substance abusers have co-occurring mental health problems, yet community-based drug treatment organizations are often not equipped to address such clinical complexity.4. Adolescents with drug abuse problems are a growing special needs population. "Yet few are able to receive treatment from a single source (p. 34)." The proposed study addresses these gaps between research and practice by using four multisystemic therapy (MST) provider organizations (including 22 therapists treating approximately 126 youths) as a platform for evaluating the effectiveness of an intensive quality assurance system in promoting the implementation of an evidence-based practice (i.e., contingency management) to treat marijuana abusing adolescents in community-based organizations. To the best of our knowledge, the proposed study is the first to examine the implementation of an evidence-based treatment of adolescent substance abuse in community-based treatment organizations. The successful dissemination of evidence-based treatments is likely to rest, in part, on the ability to maintain intervention fidelity in community contexts. Thus, the proposed research focuses on strategies (i.e., an intensive quality assurance protocol) to sustain treatment fidelity in such contexts. To facilitate a strong test of the quality assurance protocol and limit confounds associated with the initial introduction of an empirically validated treatment to practitioners, only organizations that have already implemented at least one evidence-based practice will participate in the study. Specifically, this study:Aim 1: Examines the capacity of a specified quality assurance protocol to promote therapist fidelity to contingency management in the treatment of marijuana abuse in adolescents, using a design in which MST provider organizations are randomized to contingency management intensive quality assurance versus a standard 2-day workshop in contingency management with access to additional consultation, but no sustained quality assurance.Aim 2: Evaluates the association between therapist fidelity to contingency management and youth marijuana use.Aim 3: Examines possible youth, therapist, and organizational moderators of (a) the effects of intensive quality assurance on therapist fidelity to contingency management, and (b) the effects of therapist fidelity on youth outcomes.